Superficial fungal infections in humans are of three major types: (a) superficial candidiasis, produced by Candida albicans; (b) tinea versicolor, produced by Pityrosporum orbiculare; and (c) dermatophytosis, produced by dermatophytic fungi of the genera Trichophyton, Microsporum, and Epidermophyton. Certain persons seem to have a predisposition to one or more of these organisms and develop chronic infections which can last for years. In many, but not all cases, this predisposition seems to be related to defects in cell-mediated immunity against the infecting organism. In addition, the propensity to produce chronic infections may be a characteristic of the organisms themselves, and appears to be inversely related to the amount of inflammation produced in the lesions. Some of the studies outlined in this proposal are directed at evaluating the inflammation-producing capacity of these organisms in an effort to determine the mechanism by which inflammation is produced in the infected skin. Others are aimed at examining defects in cell-mediated immunity present in patients with chronic superficial fungal infections in an attempt to define the underlying mechanisms. Since some previously-described mechanisms of immune dysfunction may be potentially reversible in vivo, we may be able to identify subsets of patients who might benefit from therapy aimed at the underlying defect. In addition, since patients with superficial fungal infections are usually in otherwise good health, they make up an excellent population in which to study naturally occurring immune defects. The findings in these studies may be applicable to other, more serious conditions where similar immune defects may play an important role in the disease process.